The Fontan procedure offers a means of palliating the hemodynamic derangements associated with some complex congenital heart lesions. The result, in most cases, is a chronically elevated systemic venous pressure. We propose to perform a battery of noninvasive tests of hepatic function in patients who have undergone the Fontan procedure in an attempt to define the prevalence and pattern of hepatic dysfunction (possible effect of systemic venous hypertension on the liver) in this population of patients.